Title: Far-field OTR and ODR images produced by 7-GeV electron beams at APS.

Abstract

We have investigated the angular distribution patterns (far-field focus) of optical transition radiation (OTR) and optical diffraction radiation (ODR) generated by 7-GeV electron beams passing through and near an Al metal plane, respectively. The 70-murad opening angles of the OTR patterns provide calibration factors for the system. Effects of the upstream quadrupole focusing strength on the patterns as well as polarization effects were observed. The OTR data are compared to an existing OTR single-foil model, while ODR profile results are compared to expressions for single-edge diffraction. ODR was studied with impact parameters of about 1.25 mm, close to the gamma lambda-bar value of 1.4 mm for 628-nm radiation. We expect angle-pointing information along the x axis parallel to the mirror edge is available from the single-lobe ODR data as well as divergence information at the sub-100-murad level. Experimental and model results will be presented.

We have continued our investigations on imaging 7-GeV electron beams in a transport line at the Advanced Photon Source (APS) using optical transition radiation (OTR) and optical diffraction radiation (ODR) emitted from an Al blade. In our experiments appreciable visible wavelength ODR is emitted for impact parameters of 1 to 2 mm, values that are close to {gamma}{lambda}/2{sub {pi}}. We have now upgraded our imaging system to include an optical transport that provides either near-field or far-field imaging, and we have performed initial experiments. The OTR far-field images indicate that beam divergence effects at the 30-70 microrad regime are detectable,more » and these are some of the first recorded for this regime. An analytical model predicts beam-size sensitivity in the 20-50 micron regime, while beam position resolution to 10 microns with a smaller beam and higher optical magnification should be feasible with near-field ODR imaging. Although originally developed to support top-up operations at APS, the ODR imaging techniques for nonintercepting relative beam size and position monitoring should also be applicable to high-energy accelerator beams that drive x-ray FELs, energy-recovering linacs for light sources, and the proposed ILC.« less

We have continued our investigations on imaging 7-GeV electron beams in a transport line at the Advanced Photon Source (APS) using optical transition radiation (OTR) and optical diffraction radiation (ODR) emitted from an Al blade. In our experiments appreciable visible wavelength ODR is emitted for impact parameters of 1 to 2 mm, values that are close to {gamma}{lambda}/2{pi}. We have now upgraded our imaging system to include an optical transport that provides either near-field or far-field imaging, and we have performed initial experiments. The OTR far-field images indicate that beam divergence effects at the 30-70 microrad regime are detectable, andmore » these are some of the first recorded for this regime. An analytical model predicts beam-size sensitivity in the 20-50 micron regime, while beam position resolution to 10 microns with a smaller beam and higher optical magnification should be feasible with near-field ODR imaging. Although originally developed to support top-up operations at APS, the ODR imaging techniques for nonintercepting relative beam size and position monitoring should also be applicable to high-energy accelerator beams that drive x-ray FELs, energy-recovering linacs for light sources, and the proposed ILC.« less

We have successfully imaged for the first time the angular distribution patterns of optical transition radiation (OTR) generated by 120-GeV proton beams passing through an Al metal plane. These experiments were performed at Fermilab (FNAL) with the same chamber, foil, and camera design as with the near-field experiments previously reported. In this case the lens-to-CID-chip separation was remotely adjusted to provide the focus-at- infinity, or far-field optical imaging. Data have been obtained in transport lines both before the antiproton production target and before the NuMI target with particle intensities of about 5 to 22 times 10{sup 12}. A two-foil interferometermore » calculation was also performed. Single-foil experimental and modeling results will be presented.« less

We have evaluated the feasibility of using the optical diffraction radiation (ODR) generated as a 1- to 6-GeV CW electron beam passes nearby the edge of a single metal conducting plane as a nonintercepting (NI) relative beam size monitor for CEBAF. Previous experiments were successfully done using near-field imaging on the lower-current, 7-GeV beam at APS, and an analytical model was developed for near-field imaging. Calculations from this model indicate sufficient beam-size sensitivity in the ODR profiles for beam sizes in the 30-50 micron regime as found in the transport lines of CEBAF before the experimental targets. With anticipated beammore » currents of 100 microamps, the ODR signal from the charge integrated over the video field time should be ~500 times larger than in the APS case. These signal strengths will allow a series of experiments to be done on beam energy dependencies, impact parameters, polarization effects, and wavelength effects that should further elucidate the working regime of this technique and test the model. Plans for the diagnostics station that will also provide reference optical transition radiation (OTR) images will also be described.« less

We have evaluated the feasibility of using the optical diffraction radiation (ODR) generated as a 1- to 6-GeV CW electron beam passes nearby the edge of a single metal conducting plane as a nonintercepting (NI) relative beam size monitor for CEBAF. Previous experiments were successfully done using near-field imaging on the lower-current, 7-GeV beam at APS, and an analytical model was developed for near-field imaging. Calculations from this model indicate sufficient beam size sensitivity in the ODR profiles for beam sizes in the 30- to 50- micron regime as found in the transport lines of CEBAF before the experimental targets.more » With anticipated beam currents of 100 muA, the ODR signal from the charge integrated over the video field time should be -500 times larger than in the APS case. These signal strengths will allow a series of experiments to be done on beam energy dependencies, impact parameters, polarization effects, and wavelength effects that should further elucidate the working regime of this technique and test the model. Plans for the diagnostics station that will provide reference optical transition radiation (OTR) images will also be described.« less